Few antigens are well characterized in the human male reproductive system. There is a general consensus, however, that these antigens may be important for treating infertility patients and developing an immunocontraceptive. A strategy is proposed to identity functionally significant proteins for further study in the human male reproductive system. The biochemical characteristics of epididymal fluid and sperm plasma membranes may be particularly important in the distal epididymis, since it is here that sperm become mature and capable of fertilization. Using a technique of neonatal tolerization and immunosuppression to caput epididymal fluids, we are producing monoclonal antibodies that are regionspecific for caudal epididymal fluid. We will also immunize mice with detergent extracts of caudal sperm. These colonies will be screened by ELISA to be negative to testis and somatic cells, and positive to ejaculated sperm membrane preps. Antibodies will be selected for further investigation based on their ability to inhibit sperm function (motility, ability to penetrate cervical mucus and hamster eggs). Antigens recognized by these selected antibodies will be characterized by biochemical (purification and sequencing, and carbohydrate analysis), morphological (immunocytochemistry), and molecular (PCR amplification of cDNA and Northerns) studies. This project is unique in that we have an epididymal source from young organ donors who are brain dead in addition to patients from a clinical infertility practice. We have also demonstrated that the technique of tolerization and immunosuppression does enhance production of antibodies to minor antigens in caudal fluid.